This invention relates to optical telecommunications systems. The invention is particularly advantageous when applied to free-space optical telecommunications.
Free-space optical telecommunications is of recently renewed interest because steps that have been taken to reduce official regulation of the telecommunications industry make it possible from a regulatory standpoint for new telecommunications services providers to enter the service areas of other existing service providers. To economically enter new areas, however, new service providers are looking for ways to avoid having to provide expensive hard-wired connections (e.g., twisted pair wire, coaxial cable, or optical fiber) to the location of each service customer. Radio communication is not a viable alternative for the bulk of the service that must be offered because the radio bandwidth available for such use is limited and still highly regulated.
Free-space optical communication has the potential to solve the problems mentioned above. Free-space optical communication means substantially unguided, point-to-point, line-of-sight communication using light (e.g., infra-red light) passing through the atmosphere. In general, such communication is bi-directional because the communications services provider must send information to and receive information from remotely located customers.
A possible limitation of free-space optical communication is that light can only be usefully transmitted through the atmosphere over relatively short distances. Typical distances might be in the range from about 500 meters to about 1,000 meters, dependent upon quality of service. Frequent regeneration of the optical information may therefore be necessary in a system that involves greater distances. In order to keep the system economically viable there is a need for low-cost and efficient optical transceivers which may be required in substantial numbers in the system.
In view of the foregoing, it is an object of this invention to improve and simplify optical transceivers.
It is a more particular object of this invention to provide improved and simplified optical transceivers that are particularly adapted for free-space optical telecommunications.